In the meantime I have intensively dealt with the problem and at last found a solution for me with a lot of effort.

Frame type=5 means 'Explorer Frame' (Z-Wave+ only). These frames are sent by a device if it has lost routing. They are forwarded by other devices until at last is reaches the receiver. The receiver answers with the route and thus we have a self-repairing function.

It's a miracle why my device was not able to send its telegrams via the normal route. It has worked since months and nobody has changed anything. And it's not clear why the self-repairing didn't work. As you see in my first post the receiver (Z-Way) has answered the requests. Maybe because it's a battery driven device?

The huge amount of notifications messages I believe is caused by a bug in module ZWave and may be another issue.

I tried many things to bring the correct route into the device again but nothing helped. At last I made a new inclusion of the device and now it works as correct as before.
This is of course unsatisfactory and maybe someone can tell me a better way to solve this in the future.